Green strategies in formulating, stabilizing and pipeline transportation of coal water slurry in the framework of WATER-ENERGY NEXUS: A state of the art review

Abstract Advanced processing approach of coal source and their prospective developed technologies contribute a greater way on addressing the challenges due to fuel energy crisis and the utilization of the coal sources in an efficient, economical and clean way. The slurry form of the coal and its stabilization has emerged as an advanced area of research in the domain of coal processing technologies. This review attempts to cover the role of the prime factors in stabilization of coal water slurry (CWS) using additives, interaction mechanism of the additives employed with coal particle, the flow behavior of CWS. The various factors affecting the modification of interfacial characteristics of the coal, like adsorption surfactant or dispersing agent, coal particle size distribution, exposure to advanced techniques like ultra-sonication, microwave radiation and temperature, etc., that largely determine CWS stabilization are discussed. It is observed that, the different technique like green natural surfactant alone or its mixture with synthetic surfactant in the preparation of slurry can reduce the emission of harmful gases during its combustion. The critical findings including the issues on flocculation and substantial settling behavior of the coal particles was caused due to the existence of Van der Waals forces of attraction among coal particle in high concentrate coal water slurry (HCCWS), the minimization of slurry viscosity during pipeline transport for easing on the flow behavior and the behavior of HCCWS like liquid fuel during combustion and is economical viability is comprehensively discussed and summarized.